The various embodiments disclosed herein are directed to a mounting device and method for securing an aerodynamically shaped seat post to a seat tube of a bicycle.
Traditional bicycles are typically fabricated from a metallic material such as aluminum for the purposes of balancing strength and weight. Current methods of manufacturing high-end bicycles involve the use of fabricating the various components of the bicycle including but not limited to the frame and seat post with carbon fiber material. The benefit of utilizing carbon fiber is that it is significantly lighter than aluminum. Unfortunately, carbon fiber has structural strength limitations compared to aluminum. By way of example and not limitation, carbon fiber material is more susceptible to breakage when exposed to a point concentration or a stress concentration.
In traditional aluminum bicycles, a seat post of the bicycle is connected to the seat tube in the following manner. The seat post is round and is inserted into the seat tube which has a corresponding circular tubular configuration. Moreover, the seat post is round or circular which makes these parts easy to manufacture while holding tight tolerances. Accordingly, traditional seat post have a tight fit with the seat tube. Frequently, in order to insert the seat post into the seat tube, one must initially insert the seat post into the seat tube while rotating the seat post back and forth until reaching the desired seat height. In order to lock the position of the seat height, the seat tube may have a split with a clamp that encircles the seat tube at the split. The clamp is tightened down so that the seat tube tightens down on the seat post. The clamp places forces on the periphery of the seat post. The friction between the seat post and the seat tube holds the seat post and the vertical height of the seat in position. The tight fit between the seat post and the seat tube and the round configuration prevents stress concentrations that might cause failure in the seat post or seat tube despite the high level of clamping forces created by the clamp.
As discussed, the trend in manufacturing bicycles is to manufacture bicycles from carbon fiber material due to its optimal light weight characteristic. Fortunately, since bicycles are being manufactured from carbon fiber material, the shapes of these bicycles can take on aerodynamic configurations. In other words, the seat tube and the seat post no longer need to be circular for manufacturing purposes. Rather, the seat post and seat tube may have other sleek aerodynamic shapes to reduce wind drag. Aerodynamic shapes are typically oval or oblong in cross-section. Unfortunately, due to the oval cross-section of the seat post, the clamp for mounting the seat post to the seat tube presses on the seat post unevenly thereby causing stress concentrations. As a result, bicycle manufacturers have had to increase the thickness of the carbon fiber material in order to withstand the compressive forces caused by the clamp to prevent failure of the seat post. The increased thickness causes increased weight. Increased weight causes the rider to be slower. In professional bicycle racing, a fraction of a second could mean the difference between winning and losing. Also, it is more difficult to obtain a tight fit between the seat post and the seat tube with carbon fiber. The loose fit between the seat post and the seat tube and the non-round configuration of the seat post create an environment where point concentrations are applied to the seat post and promote failure of the seat post.
Accordingly, there is a need in the art for an improved structure and method for clamping an aerodynamically shaped carbon fiber seat post to a seat tube.